Perforation tools are used for completion of an oil or gas well by blasting tunnels into the formation allowing oil or gas to flow into the wellbore. Perforation tools are often conveyed by a wireline or a downhole tractor.
A perforation tool usually comprises several charges which are to be detonated sequentially in accordance with a detonation plan. Separate relays may be used for detonation of each of the charges, or the same relay may be used for all of the charges.
Shaking and bumping of the tool during transport or a shock from the detonation of a previous charge cause the relay to first disconnect and then reconnect, and sparks are thus generated. When a spark is generated, small fragments are deposited on the pin and the contact of the relay. Therefore, the relay may not always function when needed since the amount of deposit may have become too great for electrical connection to be obtained.